Oracle architecture and backup (16) -- BG-ckpt

1. What is a ckpt process?

 

Purpose:

Send a signal to dbwn

Update Data File Header

Update Control File

 

At specific times, all modified databasebuffers in the system global area are written to the datafiles by dbwn. thisevent is called a checkpoint. The Checkpoint Process is responsible forsignalling dbwn at checkpoints
And updating all the datafiles and control filesof the database to indicate the most recent checkpoint.

 

Example 2

[Oracle @ localhost desktop] $ PS-Ef | grep ora_oracle 6491 1 0? 00:00:00 ora_pmon_orcloracle 6493 1 0? 00:00:00 ora_psp0_orcloracle 6495 1 0? 00:00:00 ora_mman_orcloracle 6497 1 0? 00:00:00 ora_dbw0_orcloracle 6499 1 0? 00:00:00 ora_lgwr_orcloracle 6501 1 0? 00:00:00 ora_ckpt_orcloracle 6503 1 0? 00:00:00 ora_smon_orcloracle 6505 1 0? 00:00:00 ora_reco_orcloracle 6507 1 0? 00:00:00 ora_cjq0_orcloracle 6509 1 0? 00:00:00 ora_mmon_orcloracle 6511 1 0? 00:00:00 ora_mmnl_orcloracle 6513 1 0? 00:00:00 ora_d000_orcloracle 6515 1 0? 00:00:00 ora_s000_orcloracle 6519 1 0? 00:00:00 ora_qmnc_orcloracle 6527 1 0? 00:00:00 ora_q000_orcloracle 6529 1 0? 00:00:00 ora_q001_orcloracle 6538 1 0? 00:00:00 ora_j000_orcloracle 6541 2720 0 00:00:00 pts/0 grep ora _ [Oracle @ localhost desktop] $ PS-Ef | grep ora _ | grep ckptoracle 6501 1 0? 00:00:00 ora_ckpt_orcl [Oracle @ localhost desktop] $ kill-9 6501 [Oracle @ localhost desktop] $ PS-Ef | grep ora _ | grep ckpt [Oracle @ localhost desktop] $ PS-ef | grep ora_oracle 6554 2720 0 00:00:00 pts/0 grep ora _ [Oracle @ localhost desktop] $ sqlplus/As sysdba; SQL * Plus: Release 10.2.0.1.0-production on Thu Jun 6 11:20:14 2013 copyright (c) 1982,200 5, Oracle. all rights reserved. connected to an idle instance. SQL> Startuporacle instance started. total system global area 838860800 bytesfixed size 1222192 bytesvariable size 788531664 bytesdatabase buffers 46137344 bytesredo buffers 2969600 bytesdatabase mounted. database opened. SQL> exit; disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0-productionwith the partitioning, OLAP and Data Mining options [Oracle @ localhost desktop] $ PS-Ef | grep Ora _ | grep ckptoracle 6568 1 0? 00:00:00 ora_ckpt_orcl

Summary

 

1. ckpt, a very important background process, cannot be killed. Trigger sequence: ckpt ------> dbwr -------> lgwr

2. Role: send a signal to dbwn, update the data file header, and update the control file

3. Run the ps command in Linux to view the ckpt process.

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